The sign language phenomenon that some scholars refer to as ‘agreement’
has triggered controversial discussions among (sign language) linguists.
Crucially, it has been argued to display properties that are at odds with
the notion of agreement in spoken languages. A thorough theoretical
investigation of the phenomenon may thus add to our understanding of the
nature and limits of agreement in natural language. In this talk, I focus
on the development of so-called agreement markers found in many different
sign languages. I argue that agreement markers provide evidence that sign
language agreement is consistently syntactic. In addition, I illustrate
that the grammaticalization of agreement markers can be accounted for by
means of syntactic and semantic mechanisms that have been independently
argued for in spoken language.